We conducted a prospective double-blind randomised trial to compare bupivacaine 0.5%; a 50 : 50 mixture of bupivacaine 0.5%/lignocaine 2% with 1 : 200 000 adrenaline (final concentration); and lignocaine 2% with 1 : 200 000 adrenaline for converting a low-dose labour epidural into a block adequate for emergency Caesarean section. Ninety patients were studied, 30 in each group. There was no difference between the groups in the time taken for bilateral loss of cold sensation to reach T4. Onset time was unaffected by the existing sensory level pre-Caesarean section top-up; the number of low-dose top-ups in labour; the total dose of bupivacaine in labour; or maternal weight or height. Three patients in the lignocaine with adrenaline group had blocks that reached the cervical dermatomes and three in the same group required general anaesthesia for inadequate anaesthesia, compared with none in the other groups (both p = 0.04).